1-Step 1: Make the Caramel Topping Heat 2/3 cup sweetened condensed milk, 1/4 cup unsalted butter (cut into chunks), 1/4 cup packed light brown sugar, and 2 tablespoons light corn syrup over medium heat until it bubbles. Simmer until the mixture thickens and turns a medium caramel color, then add 1 teaspoon vanilla extract or vanilla bean paste and 1/2 teaspoon fine salt. Let it cool to room temperature before using.

2-Step 2: Prepare the Shortbread Crust Combine 1/2 cup unsalted butter (room temperature), 1 cup all-purpose flour, 1/4 cup powdered sugar, and 1/4 teaspoon fine salt to form a dough. Press this into your lined pan and prick it with a fork. Bake at 350°F for 22-25 minutes until the edges brown, then cool and reduce the oven to 325°F.

3-Step 3: Mix and Bake the Brownie Batter In one bowl, mix 1 1/2 cups granulated sugar, 3/4 cup all-purpose flour, 2/3 cup unsweetened cocoa powder (sifted), 1/2 cup powdered sugar, 1/2 cup dark chocolate chips (chopped), and 1/2 teaspoon fine salt. In another, whisk 2 large eggs (room temperature), 1/4 cup vegetable or canola oil, 1/4 cup unsalted butter (melted), 2 tablespoons water, and 1 teaspoon vanilla extract or vanilla bean paste. Combine and pour over the cooled crust, then bake for 38-43 minutes until edges set.

4-Step 4: Prepare the Chocolate Ganache Heat 1/2 cup heavy whipping cream until bubbles form, pour over 2/3 cup dark chocolate chips (60-65% cocoa), and let sit for a minute. Stir until smooth, then add 2 tablespoons unsalted butter (room temperature), 1 tablespoon light corn syrup (optional), and 1/4 teaspoon fine salt. Cool until thickened.

5-Step 5: Assemble and Chill Spread the cooled caramel over the brownies, add the ganache on top, and sprinkle with flaky sea salt if desired. Chill before slicing with a warm, sharp knife for clean cuts. The total time is about 1 hour and 40 minutes, including cooling.